Huffing and puffing their way through a 12-week workout, the Herald's Bikini Body Guide challengers Tina and Tessa were feeling a little guilty for not doing it perfectly. But when Tina spoke to BBG founder Kayla Itsines, she was pleasantly surprised to find Itsines completely approved of their efforts.

"Eat the lasagne."

Wait, what? Did the hottest personal trainer on social media just tell us she recommended a client eat her grandmother's lasagne?

The same trainer who prescribes almost impossible sets of sit ups and lunges and squats and push ups? Who posts gravity-defying videos of her jumping from one exercise to the next? Surely she didn't get her enviable abs with servings of lasagne?

When the client - who wanted advice on what she could eat at her grandmother's house - pushed back, Kayla's answer was simple:

"Cause she's your Nonna? She may not be around for a very long time. So you might want to eat her food while you can."

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"If you're exercising and eating well most of the time, that's great if you weren't doing that a few weeks ago."

That made us feel a whole lot less guilty about what we had done months before.

Just a few weeks ago, some of us were scrolling through our social media feeds, possibly resting off food comas and fawning over pictures of Christmas presents, holiday brunches and glasses of bubbles - only to be interrupted by images of the slim and toned Itsines working out, reminding us of what will never be if we continued to imbibe in holiday gluttony.

Now, months later, after trying Kayla's workout plans, we're stronger and more confident, but also wondering what could have been if we had followed everything to the letter. We're only human, and McDonald's is a temptation we have to battle regularly (even though Kayla doesn't, she doesn't eat fast food).

After a refreshing chat with Kayla, we discovered a more candid side to the trainer, beyond the sweaty selfies and the fitspo memes. Her openness left us feeling more confident of what we've accomplished. She knows what can cause us to falter and yet she's understanding and supportive anyway.

Joining #thekaylamovement

The workouts were definitely challenging, as Tina can attest to. Photo / Supplied

Kayla Itsines is a 24-year-old trainer from Adelaide, best known for her Bikini Body Guides (or BBG for short). Her workout guides started off as PDFs outlining what she prescribed to her clients whose goals included wanting the confidence to wear a bikini on the beach. Those PDFs inspired a paid app called Sweat with Kayla, giving users workouts, menus, and background information at the press of a button.

Her Instagram account (4.7 million followers and growing) features before-and-after photos of women who have completed her workouts, and the results are compelling. What were once love handles are now abs. What were once flat faces now bear beaming smiles to accompany new muscles.

The photo evidence of how well the programme worked was enough for me to fork out roughly $5 a week for the Sweat app (or $135 for the PDF guides, in Tessa's case), if it meant that we could get sick abs like Kayla's.

So come early January, Tessa and I joined #thekaylamovement, a 12-week programme running from January to April, bringing together an online community of women who want to change their bodies and their attitudes.

To our credit, we've achieved some amazing things. I can do a push up on my toes, not my knees. My squats look amazing. Tessa can burpee harder and sit up faster. Oh, and her jump lunges look pretty on point. Our clothes fit better, our confidence has improved. And we have the admiration of our co-workers, who have followed along our fitness journey with interest.

And yet, over these last few weeks, there were times where we felt lost. Life gets in the way of scheduling the simplest 28-minute strength session.

Tessa was studying part time outside of work. I got sick early on, and there was one week where I just couldn't do it. I didn't have a great reason, I just lost my discipline. Not exactly the sort of things you want to admit to someone who is also busy, travelling the world and meeting members of #kaylasarmy, and yet still looks amazingly fit.

"You have better abs than you think"

We asked Itsines about what to do when we lost our way, and lamented that our workouts are not up to snuff. Refreshingly, when we absolved our lazy sins to Kayla, she did not take on the role of disciplinarian.

I admitted to her that it takes me three minutes to complete a set of 15 sit ups with my feet up on the coffee table. I revealed my lack of ab strength, and asked her how I could mimic her videos one day.

"Aww, that's cute," she said.

Crap. I feared some patronising coming my way. But nope. She went on to explain how she's trained new mums who need to take time to work their way through the ab workouts. "It's all about taking your time. That's why the reps are in there. It's not like you have to do them in this amount of time.

"I'm sure you've got better abs than what you say you do right now."

At this point, I'm charmed. Maybe I do have better abs than I think.

What about when we let our workouts fall by the wayside? In the middle of what's coming off as a confessional, Kayla interrupted me.

"It's so normal," she said. She should know. She's trained all sorts of women all over the world.

"I'm a girl, and I'm not wrong for wanting a day off. Or I'm not wrong for stopping the BBG for a few weeks. Or I'm not wrong for sleeping in."

Sure, but really? No guilt? No chastising us for not doing it perfectly, "Ms Perfect Abs and Smiles"?

"Every girl is like this and the sooner women realise we are all the same - we're not wrong when we don't want to do something - then I think the better our mentality becomes.

"I'm trying to make women feel better about their lifestyle. They're doing something and that is better than nothing."

Does Kayla ever throw in the towel?

Week Eight was a tough one for Tessa. Photo / Supplied

Even Kayla has days where she does not want to train and has to psych herself up to do it: "I'm like every other girl. Every other girl has those days, like no. No, I don't want to do this."

In those situations, she pulls up her partner Tobi Pearce's playlist, which features hip hop heavyweights Eminem, Lil Wayne and Kayne.

Itsines did admit there is one day a month when even hardcore hip hop can't get her motivated to visit the gym. On the first day of her period, she refuses to work out. She rests. Because this is what works for her and her body.

"There's nothing worse than exercising on your period," she said, but noted that other women may feel completely fine during their monthly cycle. "Go for a walk if you feel like it. But I'm realistic. If you feel like it, if you want to, then do it. If you want to rest, rest.

"I'm not going to tell you to push through and just do it, because I'm not doing it myself."

And with that, a couple of candid confessions from the woman with the best abs on Instagram, we feel less focused on where we've faltered. We can focus more on the gains made.

If Kayla's goal is to empower women and create a positive lifestyle change, our candid chat has done wonders for at least the two of us.

How to do BBG, according to Kayla

• I've been sick or I've fallen off the horse. Should I move on to the next week's workouts?

"Keep going from the day you missed out. Repeat that week. The only reason I say that is if you need to rest, I'm not going to go 'you need to finish that week'. Definitely rest for a week if you're sick or whatever, go back and do those two sessions."

• I'm on my first day of my period and I feel awful. Should I work out?

It depends. "It's up to the individual. My best friend, she has her period and she feels nothing. She's like, I don't feel anything. I don't have a headache. I don't feel dizzy. I feel motivated, just as motivated today as I did the other day. It's about listening to yourself and your body. For me, the day that I get my period, there's no way I'm working out. Absolutely not. I rest. That's just me and that's my body.

"It's about being careful with your body and recognising the signs and if you're feeling dizzy or you're feeling sick or you're feeling like you're in pain, or you need a heat pack, you need to rest. Not push through."

• What is your least favourite workout?

High-intensity interval training sessions: 15-minute sessions that involve sprinting for 30 seconds, then 30 seconds of rest. "For some reason my phone always ends up falling off the treadmill, running down the treadmill, going onto the ground where I have to get it. I just don't like the running, there's no one around me, I'm just by myself in the times I've booked in my HIIT training